Too many diet drinks may spell heart trouble for older women

Healthy postmenopausal women who drink two or more diet drinks a day may be more likely to have a heart attack, stroke or other cardiovascular problems, according to new research from the University of Iowa.

The research, which was presented on 30 March 2014 to the American College of Cardiology’s 63rd Annual Scientific Session, found that, compared to women who never or only rarely consumed diet drinks, those who consumed two or more were 30 per cent more likely to suffer a cardiovascular event and 50 per cent more likely to die from related disease.

“Our findings are in line with and extend data from previous studies showing an association between diet drinks and metabolic syndrome,” said Ankur Vyas, MD, Fellow of Cardiovascular Diseases at the University of Iowa Hospitals and Clinics and lead investigator of the study. “We were interested in this research because there was a relative lack of data about diet drinks and cardiovascular outcomes and mortality,” he said.

Study method

Researchers analysed diet drink intake and cardiovascular risk factors from 59,614 participants in the Women’s Health Initiative Observational Study, which they said made this the largest study to look at the relationship between diet drink consumption, cardiac events and death.

Information on women’s consumption of diet drinks was obtained through a questionnaire that asked them to report their drink consumption habits over the previous three months. This information was assessed at follow-up year three of the Women’s Health Initiative Observational Study.

Each drink was defined as the equivalent of a 12-ounce beverage and included both diet sodas and diet fruit drinks. For the purposes of the analysis, researchers divided the women into four consumption groups: two or more diet drinks a day, five to seven diet drinks per week, one to four diet drinks per week, and zero to three diet drinks per month.

After an average follow-up of 8.7 years, the primary outcome — a composite of incident coronary heart disease, congestive heart failure, heart attack, coronary revascularisation procedure, ischemic stroke, peripheral arterial disease and cardiovascular death — occurred in 8.5 per cent of the women consuming two or more diet drinks per day, compared to 6.9 per cent in the five-to-seven drinks per week group; 6.8 per cent in the one-to-four per week group; and 7.2 per cent in the zero-to-three per month group.

Researchers said the association persisted even after they adjusted the data to account for demographic characteristics and other cardiovascular risk factors and comorbidities, including body mass index, smoking, hormone therapy, physical activity, energy intake, salt intake, diabetes, hypertension, high cholesterol and sugar-sweetened beverage intake. Women who consumed two or more diet drinks a day were younger, more likely to be smokers, and had a higher prevalence of diabetes, hypertension and higher body mass index.

The average age in their study was 62.8. To be included in the analysis, women had to have no history of cardiovascular disease and be alive 60 or more days from the time of data collection.

Results raise more questions

But the researchers said the association between diet drinks and cardiovascular problems raised more questions than it answered, and should stimulate further research.

“We only found an association, so we can’t say that diet drinks cause these problems,” Dr Vyas said.

“It’s too soon to tell people to change their behaviour based on this study,” Dr Vyas said. “However, based on these and other findings, we have a responsibility to do more research to see what is going on and further define the relationship, if one truly exists,” he said.

“This could have major public health implications,” Dr Vyas said.

About one in five people in the US consume diet drinks on a given day, according to data from the National Health and Nutrition Examination Survey (2009-2010). But the University of Iowa researchers cautioned that their study only applied to postmenopausal women.

Previous studies have found artificially sweetened drinks to be associated with weight gain in adults and teens, and seem to increase the risk of metabolic syndrome, which makes both diabetes and heart disease more likely.

Dr Vyas said future research could include clinical studies, animal models and even molecular and pharmacologic analyses to begin to explain what, if any, direct role diet drinks play in heart health.